Precipitating Help Needed for New Guy

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clownfish

Member
Joined
Sep 8, 2015
Messages
5
Hi everyone, here's a post from another new guy needing a little help.

Okay, so I took my maiden gold run yesterday, after studying various posts and tutorials on the forum, I set myself up with a Sulfuric Cell and started stripping my gold plated electrical connectors, everything went fine from what I can see except the precipitation, I'll go through the steps I took so anyone who wants to help me can see what I did as maybe I made a mistake earlier in the process and didn't notice until the gold wouldn't drop.

I put the connectors in a metal basket (I think it's brass or copper, it wasn't oxidizing green so I had my doubts about it being copper, but it was conductive as tested with a multimeter).

Filled my pyrex pan with 96% sulfuric acid and put my lead cathode on the other side of the pan, hooked the negative to the cathode (duh) and the positive to the basket.

The gold came off the connectors and the black powder build up in the acid, just as described, I repeated the process until the circuit started to short from all the gold in the acid, then I took the basket and cathode out and let the dust settle (literally) for about 30 minutes to an hour.

I then poured off the top of the acid into a glass jar for later use and was left with about 1/8" deep muddy mixture of powder and acid, I poured this into about 1 liter of water and stirred it up, let it settle for about another half an hour and then filtered it (coffee filters from the grocery store).

This went fine and I was left with a bunch of black coffee filters and some black/greyish water (which means all the black gold didn't come out, so I saved this for later refinement, I was just trying to go through the whole process once, learn from some mistakes and improve it (as I have a LOT of electronics to process).

I then mixed my 5% Chlorine Bleach with 33% Hydrochloric Acid (1:2 Respectively), ran from the fumes ( I did it outside and I humbly admit that I was wring thinking that the people saying how you need a fume hood were just prudes - I am now a firm believer in Fume hoods and I'm building one before I continue.)

I soaked all the coffee filters in that and watched the black disappear and turn a golden yellow color. I am now assuming that this is the AuCl[3].

This is as far as I got, at this point I tried a couple different things to precipitate the gold with small amounts of the yellow liquid (4 ounces or so), none of which worked and now I am stumped, here's what I tried.

I mixed some SMB with distilled water until saturated and then poured some of it into the AuCl[3], it immediately turned clear, but no flakes. It was about 60 degrees in the garage I was working in and I thought this might be a bit too cold, so I put the beaker next to my heater to warm a little and it started bubbling and then turned a murky greenish-brown color, from there, nothing, I added more SMB and stirred, it started fizzing and even overflowed, the solution just got darker and then stopped reacting to the SMB, it should be noted that the offensive Sulfur smell was definitely present in mass, I had to leave te garage a couple times as I couldn't take it and the fan that I had put in wasn't carrying it out fast enough (as stated before, building a fume hood - learned my lesson) then I read a few more threads on the forum and someone recommended adding the SMB to the AuCl[3] dry:

So, I took another beaker and put about 4 ounces of the AuCl[3] into it, then I poured a bit of dry SMB powder in it, it turned brown, I stirred, no flakes, added a bit more, more stink, more opaque, no flakes, eventually it stopped reacting and I gave up.

Will reply with some photos (as they're on my phone and I'm on my computer) for what it's worth, any advice on how to precipitate the gold and any corrections to my process as a whole, very appreciated.

Thanks, clownfish
 

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I am now assuming that this is the AuCl[3].
Click to expand...
Did you test your solution with SnCl to see if there was even any gold present before attempting to drop out of solution? There's a possibility that there is still too much chlorine left from the bleach. Either let the solution set for 24hrs or heat the solution to steaming, but not boiling, let cool. This should rid the solution of excess chlorine. Then add more SMB and see if you get a reaction.
 
You need to redo that basket. What you have their is a Faraday cage.
Search Faraday cage in the google search bar at the top of this apge.
 
Food for thought:

Making your basket out of an unknown material is a mistake. Use only known materials when working with these processes or you set yourself up for catastrophic failures.

Allow your gold to settle for at least a day in the future, not 30 minutes.

Rinse your gold powder with several changes of water to better remove the sulfuric acid.

I'm not sure why you ended up with "a bunch of black coffee filters".

When you use HCl and Clorox, you should add the Clorox in small increments, using only enough to dissolve the gold. Adding it all at once in a 1:2 ratio just wastes chemicals and creates a toxic cloud of chlorine gas. Remember that using a fume hood just blows the fumes away from you, but without a scrubber, they're still blowing toward anyone downwind. Be considerate of your neighbors, their pets, and the wildlife and vegetation around you.

Gold dissolved in HCl creates HAuCl4.

You didn't mention getting rid of the excess chlorine before trying to precipitate. That may be one of your problems.

We usually add the SMB to the pregnant solution, using only what is needed. Overuse of SMB will result in a dirty drop.

Gold rarely forms flakes when precipitated. More like fine powder, that may agglomerate into larger particles.

That offensive sulfur smell is sulfur dioxide (SO2). It's poisonous! You don't want to be breathing it or smelling it.

You should NOT be doing this in your garage!

When gold is precipitated from dilute solutions, it can take a long time to settle.

As Palladium has mentioned, your basket is a Faraday cage. It should be low on the side toward your cathode, otherwise the electric current tends to take the path of least resistance, traveling directly from the side of the basket to the cathode, wasting current and further degrading your basket.

Dave
 
Not trying to be the bearer of bad news, but i'm not sure it was gold. I think the material he's using is iron screen mesh for a window. I believe it may be dissolving and fouling the cell. If the basket is a Faraday then the basket would be attacked as a anode before the material inside it would or both at the same time. He may has dissolved some gold in the process, but i'm betting on it being more than gold. He said it was 1/8 in deep. Looking at that bowl that would be a lot of gold. My next question would be how much material in lbs did you run through the cell? Then again if you had used sncl we would know the answers to this. Two things are wrong with that basket. It's not copper and it's a Faraday cage.
 
Thanks for all the responses guys.

Here's the answer to your questions:

The basket isn't steel or iron, it's definitely non-ferrous as there's no rust and it's been sitting in a humid garage for a while - I think it's brass, I'm going to get a hold of some copper mesh and make an appropriate basket.

By "Black Filters" I meant the coffee filters with the black powder caught in them.

The gold definitely came off as the connectors were totally stripped when I was done, however, it took almost an our for them all to strip, so there's probably a bunch of other metals in there.

I think I'm going to go with the method described in the first reply I got in the future, but my final question remains - can I salvage the solution I have?

Thanks, clownfish
 
maynman1751 said:
I am now assuming that this is the AuCl[3].
Click to expand...
Did you test your solution with SnCl to see if there was even any gold present before attempting to drop out of solution? There's a possibility that there is still too much chlorine left from the bleach. Either let the solution set for 24hrs or heat the solution to steaming, but not boiling, let cool. This should rid the solution of excess chlorine. Then add more SMB and see if you get a reaction.
Click to expand...

Like Maynman1751 said, test with stannous to see if there is any gold in the Solution. If you don't have stannous here is a great video how to make it:

https://www.youtube.com/watch?v=659G75Kc3F0
 
clownfish said:
The basket isn't steel or iron, it's definitely non-ferrous as there's no rust and it's been sitting in a humid garage for a while - I think it's brass, I'm going to get a hold of some copper mesh and make an appropriate basket.
Click to expand...


I think that basket is stainless steel screen which is why it is non-magnetic & does not rust

Looks to silver/gray to be brass - maybe just the lighting in the pic - brass would have a yellow color to it

Drop of nitric would tell you - if its brass you will get a reaction & the acid will turn blue/green -- SS will NOT react

Kurt
 
Thanks everyone for your help and advice.

I think I'm just going to go for selling it as is and let someone with a larger operation take care of it.

Really appreciate everyone's assistance.
 

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